1. Field of the Invention
This invention relates to a grid structure for a suspended ceiling and more particularly to the connections at the intersections of the grid.
2. Background Information
Prior Art Grid
Suspended ceilings having a grid structure of intersecting, connected, beams that support acoustical panels within rectangular enclosures formed by the grid, are used extensively in commercial and industrial buildings. Such a ceiling is shown in the U.S. patents referred to below.
The prior art grid involved in this invention has main beams extending along the length of the ceiling, parallel to one another. Such main beams are suspended from a structural ceiling by hanger wires. The main beams generally are four feet (4 ft.) apart, and are connected by 4 ft. cross beams extending between, and perpendicularly to, the main beams, at two foot (2 ft.) intervals along the main beams. The grid has additional cross beams, 2 ft. in length, extending between, and connected to, the middle of the 4 ft. cross beams. The result is a grid with 2 ft.xc3x972 ft. square openings, into which correspondingly sized panels are laid.
The present invention relates to the connections at the intersections of the grid. Such connections are shown in U.S. Pat. Nos. 5,839,246, 6,178,712, and 5,517,796, incorporated herein by reference. A connector in such a connection is installed by a stab-in motion and has a stop that abuts the web of beam through which the connector is inserted. The invention involves the positioning of this stop.
Prior Art Installation of the Grid
In installing a prior art grid, a main beam section, generally twelve feet (12 ft.) in length, is assembled end to end with another main beam section to form a continuous main beam that extends lengthwise in the ceiling, parallel to one of the side walls. Each of the sections of the continuous main beam is suspended from the structural ceiling by hanger wires anchored in the structural ceiling.
Another continuous main beam is then assembled parallel to the first continuous main beam 4 ft. away from the first continuous main beam. Four foot (4 ft.) cross beams are then connected between the parallel continuous main beams perpendicularly to the main beams at two foot (2 ft.) intervals lengthwise along the main beams. Two foot (2 ft.) cross beams then are inserted between the 4 ft. cross beams at the middle thereof to form 2 ft. square openings to receive panels. Such construction is very well known. An example of such ceiling and beams is shown, for instance, in the ""246 and ""712 patents.
Prior Art Connections in the Grid
In the prior art connections, as seen for instance in the ""712, ""246 and ""796 patents, opposing connectors in a connection are connected to each other, and are connected to the web of the intersecting beam through a slot in the web. They are assembled in a stab-in motion.
In a prior art ceiling grid having 2 ft. by 2 ft. openings, the connectors at the end of both the 2 ft. and 4 ft. cross beams are the same in a given ceiling, and involve a clip or tongue at the end of the cross beam that is inserted through an opening in the web of the main beam, in the case of a 4 ft. cross beam, or through an opening in the web of a 4 ft. cross beam, in the case of a connector on the end of a 2 ft. cross beam. Again, examples of such connectors are shown in the above referred to ""712, ""246 and ""796 patents.
The 4 ft. and 2 ft. cross beams with their connectors, serve, in the case of the 4 ft. beams, to space the beams to which they are connected, from one another, in the plane of the ceiling, and, in the case of both the 4 ft. and 2 ft. cross beams, to provide a horizontal support for the acoustical panels inserted in the openings between the beams.
In a completed assembly of beams, a grid with defined 2 ft. by 2 ft. openings to receive panels, is formed. The main beams are desirably positioned substantially parallel to one another at a relatively precise 4 ft. distance, with desirably relatively tight connections, since any error in spacing because of the 4 ft. cross beams becomes cumulative across the ceiling, so that no longer is the grid a pattern of precise 2xc3x972 ft. square openings in the final assembly.
Tight, tighter, and tightness as defined herein refers to the possible lateral motion of the web that can occur in a connection. Less lateral motion of the web can occur in a tighter connection than in a looser connection.
The prior art connectors of the type referred to herein are, in a connection, not only connected to a web of a beam in an intersection, but connected to each other. The present invention has no effect on the tightness or looseness with which the connectors in a connection are connected to one another, but only has an effect on the possible lateral, or sideways, movement of the web of the beam through which the connectors pass. Again, reference is made to the ""246, ""712 and ""796 patents which explain in detail the above.
Prior Art Installation of the Connections in a Grid
Although relatively tight connections between the 4 ft. cross beams and main beams are desirable in a grid in the spacing of the main beams from one another to avoid a cumulative error across a ceiling, as explained above, relatively loose connections are desirable in the connections between the 4 ft. cross beams. In the installation of first the main beams, and then the 4 ft. cross beams, fixed 2 ft.xc3x974 ft. openings are created. It is only necessary for the 2 ft. cross beams to be connected to the 4 ft. beams in order to support the inserted panels, and not to space the 4 ft. cross beams in the plane of the ceiling.
There is not only no need for the 2 ft. cross beams to space the 4 ft. beams in the plane of the ceiling, but a need that no such spacing occur. Should, for instance, the 2 ft. cross beams be slightly too long or slightly too short, or if the spacing between openings in the main beams be slightly off from 2 ft., by using a relatively tight connection, the 2 ft. cross beams would bow the 4 ft. cross beams when connected in a given 2 ft.xc3x974 ft. opening during the construction of the ceiling. This bowing would become cumulative down the row of 4 ft. cross beams extending between a pair of parallel main beams. By creating a relatively looser connection between the 4 ft. cross beams and 2 ft. cross beams, the 2 ft. cross beams are allowed to in effect float longitudinally in the connection, without bowing the 4 ft. cross beams, whereby any errors in the manufacturing of the 2 ft. cross beams, or the spacing of the 4 ft. cross beams down the length of the main beams, can be tolerated.
Thus, there is a conflict in the requirements for tightness or looseness in the connections in a grid ceiling having 2 ft. by 2 ft. openings.
A solution to the problem would appear to be the use of two different kinds of connectors; a loose type and a tight type. The prior art, however, uses the same connector on both the 4 ft. and 2 ft. sections since manufacturers need the relative simplicity of producing, storing, and selling one type of cross beam connector in a given ceiling, and installers need to avoid confusion in the installation which could arise from using different types of connectors.
The prior art has settled on using the more loose standard in all the connections in a ceiling grid having 2 ft.xc3x972 ft. openings, since such standard can be accommodated in both the connection at the main beam, and the connection of the 2 ft. cross beam to the 4 ft. cross beam, even though the looser standard may give rise to displacement of the main beams. The tighter standard would create bowing of the 4 ft. cross beams, which would become cumulative.
The present invention provides for relatively tighter main beam connections at the end of the 4 ft. sections with relatively looser connections at the end of the 2 ft. cross beams, to the 4 ft. cross beams, with the same connector. This is accomplished by slightly moving the stop, in prior art connectors of the stab-in type shown in the ""246, ""712 and ""796 patents, a distance, for instance, of 0.005xe2x80x3xc2x10.001xe2x80x3, closer to the web of the beam to which the connector is secured, in a connection to a main beam, than in a cross beam connection to a 4 ft. cross beam. Since a connector is inserted from each side of the web, the tightness in a main beam connection is twice increased, for instance, by a greater tightness of 0.010xe2x80x3xc2x10.002xe2x80x3 in the above example, over the tightness of the connection of a 2 ft. cross beam to a 4 ft. cross beam. In a long stretch, such increased tightness at each main beam connection avoids a substantial drift in the spacing of the main beams.
In making the main beam connection tighter, the present invention utilizes the ability of the main beam to move relative to one another during the installation of the 4 ft. cross beams.
In the present invention, wherein connections at the end of the 4 ft. sections are made tighter than the connections at the 2 ft. sections, the connectors themselves are of the same configurations, and are manufactured with the same machine tools, presses, and dies in the same process. It is merely necessary to alter the stop dimensions in the dies that stamp out the connectors, to achieve the desired stop positions set forth above. The connectors are installed in the same way.